Decolorization of alkaline-earth-metal thiocyanate solutions



Patented Nov. 13,1928.

UNITED STATES PATENT OFFICE.

sonar 3.. rum-N, or wrnxmsnune, PENNSYL ANIA, nssrc son FIO ran xorrfins 'courm, A conronarron or rrmnsnvmm.

DECOLOBIZATION 01E ALKALINE-EARTH-METAL THIOCYANA'IE SOLUTION.

N0 Drawing.

This invention relates to a process for decolorizing solutions of alkaline earth metal thiocyanates, and especially calcium thiocyanate solutions used assolvents for cellulose removal of hydrogen sulphi e and hydrogen cyanide by means of alkaline absorbent solutions. It has been observed, however, that calcium thiocyanate prepared from -such material contains slight amounts of dye or coloring matter, generally red, and exceed-.

ingly difficult to remove. While such foreign material is unobjectionable for many purposes, for others it has been found tobe troublesome. For example, in processes for preparation of viscose, in which calcium thiocyanate solutions are used as solvents for cellulose, this colorin matter or dye will have the ObVlullS undesirable effect of coloring the viscose roduct. p

5 An 0 ject of my invention is to provide a process whereby such coloration maybe elim1- nated.

A further object of m invention isto provide a process of elimmatin such dye or coloring matter in calcium thiocyanate solutions,: irrespective of the use to which such solutions are put. Y

It is known that the presence of formaldehyde or the like will not diminish the solvent properties of calcium thiocyanate solutions with res set to cellulose and that it may actuall aid in the solution of cotton and the like. have found that the addition of formaldehyde sodium formate or any similar anal- ,0 ogous substance, to a calcium thiocyanate solution accompanied by heating, effectively eliminates such dye or colorin matter and produces a substantiall color ess product. I have also found that t is action is particularly effective when cellulose is present in the solution. It is known that the presence of frmaldehyde or the like in the VISCOSB prod:

not is not deleterious.

My invention is not limited to the s ecific compounds recited above. Substantia y any derivatives of any of the lowerfatty acids may be used with good results. The salts, Y esters and aldehydes of formic and acetic acids may be cited by way of example. However, I prefer to use a derivative of formaldehyde.

Application filed December 81, 1926. Serial No. 158,422,

formic acid, such as formaldehyde or sodium formats. 1 v f d In practicing my invention, I add from 1 to 5%. by volume of'a 40% formaldehyde solution or from 3 to 5% solution by weight so of sodium' formate or the equivalent thereof to a calcium thiocyanate solution of suitable strength for the solution of cellulose. The desired amount (generally 4 'to 5% by weight)" of cotton or other cellulose is then added and the whole is heated to from 120 to 130 C. and maintained at such temperature until the color of the solution, has disappeareds This generally requires one hour.

By means-of my process, the ver trou- 7o. blesome dye in calcium thiocyanate so utions, especially those solutions prepared from gas purification liquors, may be eliminated at very little expense. Furthermore, my invention makes it possible to produce practically 76 colorless solutions of cellulose or viscose by the use of calcium thiocyanate solutions.

My invention'is not limited to the-specific example herein given by way of illustration but ma 'be variously embodied within the so scptpe o the following claims.

claim as my invention:

1. The process of decolorizing a solution of an alka ine earth metal thiocyanate which comprises adding thereto a derivative of a s5 water-soluble fatty acid.

Y 2. The rocess of decolorizing a solution of an alka ine earth metal thioc anate which comprises adding thereto a erivative of formic acid.

3. The process of decolorizing an alkaline earth metal thiocyanate solution which comprises heating the same in the resence of a erivative ofa water-soluble atty acid.

4. The process of decolorizing an alkaline earthmetal thiocyanate solution which com-- prises heating the same in the presence of a erivative of formic acid.

5.'The process of decolorizing a solution of calcium thiocyanate which comprises adding formaldehyde thereto.

6. The process of decolorizing calcium thiocyanate solutions which comprises heating t e same in the presence of formaldehyde.

The process of decolorizjng a solution of calcium thiocyanate which comprises adding thereto from 0.4 to 2.0% by volume of 8.- The process of decolorizing a solution of calcium thiocyanate which comprises heatinthe ing the same to a temperature of from 120 at that temperature until the coloration disappears.

9. The process of decolorizing a solution of an alkaline earth metal thiocyanate'containing cellulose in solution which comprises adding thereto a derivative of a water-soluble fatty acid.

10. The process of decolorizing a solution of an alkaline earth metal .thioc anate containing cellulose in solution whic comprises addin thereto a derivative of formic acid.

11. e process of decolorizing a solution of calcium thiocyanate containing cellulose in solution which comprises adding formaldehyde thereto.

12. The process of decolorizing calcium thiocyanate solutions containing cellulose in solution which comprises-heating the same resence of formaldeh de.

13. he process of decolorizing a solution of calcium thiocyanate containing cellulose in solution which comprises adding thereto from 0.4 to 2.0% by volume of formaldehyde.

14. The process'of decolorizing a solution of calcium thiocyanate containing cellulose in solution which comprises heating the same to a temperature of from 120 to 130 C. in the presence of from 0.4 to 2.0% formaldehyde and maintaining the solution at that temperature until the coloration disappears.

15. The process of obtaining a colorless solution of cellulose which comprises dissolving the cellulose in a solution of calcium thiocyanate containing formaldehyde and heatin the solution thus formed until it becomes co orless.

16. The process oi obtaining a. colorless solution of cellulose which com rises dissolving the cellulose in a solution 0 calcium thiocyanate containing formaldehyde and heating from 120 to 130 C. the solution thus formed until" it becomes colorless.

In testimony whereof, I have hereunto subscribed my name this 29th day of December 1926.

ROBERT R. FULTON. 

